The present invention relates to workpiece controlling devices for sewing machines having a workpiece feed mechanism adapted to feed material in a substantially straight line.
Automatic workpiece alignment devices having controlled alignment means which can move transversely of the direction of feed of the material are described, for example, in German patent specification No. 29 48 498. The alignment means of this device is, however, outside the sewing machine and is disposed far from the point of stitch formation of the sewing machine in a tensioning device, and moves continuously in the direction of feed of the material, although the feed of material in the sewing machine takes place intermittently. Although this results in an intensive displacement of the edge of an opening of a tubular workpiece transversely of the direction of sewing, it is not suitable for controlling and aligning finite flat workpieces, and, because of the large number of alignment elements, it is an expensive construction.